The present invention relates to a fuel injection valve for use with an internal combustion engine and, more particularly, to a fuel injection valve which has plural fuel injection holes, each injecting swirling fuel to promote atomization of the fuel, and which can control the spray pattern.
A fuel injection valve set forth in JP-A-2008-280981 is known as a conventional technique for achieving promotion of atomization of fuel sprayed from plural fuel injection holes and controlling the spray pattern by making use of swirling stream.
This fuel injection valve has a valve body capable of being opened and closed to permit and stop injection of fuel, a seat portion capable of being brought into intimate contact with the valve body to stop injection of fuel, and an orifice plate disposed downstream of both the valve body and the seat portion and having fuel injection holes from which fuel is ejected. Atomized, curved swirling spray is ejected from the fuel injection holes.
Furthermore, in this fuel injection valve, the orifice plate has the fuel injection holes from which fuel is sprayed, a swirling chamber in which fuel is swirled, and a fuel intake passage for introducing fuel into the swirling chamber. The center of each fuel injection hole is offset a different amount from the center axis of the fuel intake passage. The fuel injection hole having a smaller amount of offset sprays atomized fuel over a smaller angle. The fuel injection holes having larger amounts of offset provide plural sprays of swirling and curved atomized fuel.
Owing to this configuration, the amount of fuel adhering to the intake valve (bottom) of the engine and to the inner wall surface of the cylinder is reduced. As a result, a homogeneous air-fuel mixture is produced. Hence, a decrease in the amount of soot contained in the exhaust gas and higher engine output can be accomplished.
On the other hand, a fuel injection valve set forth in JP-A-2001-317434 is known as a conventional technique for obtaining a highly atomized spray by making use of a swirling force.
In this fuel injection valve, the outer surface of each fuel injection hole for ejecting swirled fuel on the exit side is formed by first and second surfaces. The first surface includes the exit of the fuel injection hole. The second surface is spaced from the fuel injection hole, has a wall opposite to the ejected spray, and protrudes from the first surface. Thus, the ejected spray consists of a central portion and an outer portion. The outer portion is composed of a thick spray portion having a wide spread circumferentially and a thin spray portion having a narrow spread. As a result, the spray is shaped in an integrated flattened form.
This flattened spray form permits the thick spray portion having a wide spread to be directed toward the inner wall surface that is opposite to the inner wall of the intake pipe on which a fuel injection valve is disposed. Furthermore, the thick spray portion can be symmetrically directed toward the central partition wall located in the center of the intake valve. Consequently, fuel and air can be mixed efficiently while suppressing fuel deposition on the inner wall surface of the intake pipe. Thus, purification of exhaust emission and improvement of the fuel consumption can be accomplished.